I wrote an icdiff-based pretty diffs pytest plugin for internal use, and ran into the same issue. I ended up grabbing the terminal width at module-level, as well. I think I went spelunking in the GH issues and found a glimmer of possibility in the notion that get_terminal_width() returns incorrect information from within the assertrepr hook, because it's called when terminal capturing is enabled — perhaps even just a wrapped stream?
Here's the note I left myself: # This is done during initialization, before any tests are run, instead of # within our assertrepr hook — because the assertrepr hook is called while # terminal capturing is enabled and all calls to get_terminal_width() return 80 # ref: https://github.com/pytest-dev/pytest/issues/4030#issuecomment-425672782 INITIAL_TERM_WIDTH, INITIAL_TERM_HEIGHT = util.get_terminal_size() (Where util.get_terminal_size() just comes from this gist <https://gist.github.com/jtriley/1108174>) I wonder if a tool like screen or tmux could supply real sizing info and resize events, while also appearing like an unwrapped stream — and perhaps its output could be saved & compared against. Cheers, Zach On Wed, Apr 8, 2020 at 4:55 PM Floris Bruynooghe <f...@devork.be> wrote: > Hi Harry, > > To the best of my knowledge you stumbled into a hard and dark corner of > pytest. IIRC previous attempts at improving this have not gone too > well. But like this always goes, it sounds like you've set yourself up > to be the expert now and are in a great position to clean this up and > make it work nicely for people. ;) > > Cheers, > Floris > > On Tue 07 Apr 2020 at 19:26 +0100, Harry Percival wrote: > > > cf discussion here https://github.com/pytest-dev/pytest/issues/162 > > > > I'm working on pytest-icdiff, trying to get it to print out well > optimised > > messages for different terminal sizes, and it's hard. > > > > when i'm running tests using runpytest, and I _think_ in real life too, > > config.get_terminal_writer().fullwidth *inside the hook* is returning > > incorrect values: resizing the terminal i'm using to run the tests has no > > effect on the value i get from it. and when I use that value irl, real > > test output does not adjust correctly to the terminal size > > > > but calling py.io.TerminalWriter().fullwidth _outside_ the hook, eg at > > module level, _does_ give me readings that look right. but testing that > > is hard. > > > > intriguingly, if I do testdir.monkeypatch.setenv('COLUMNS', '50'), then > the > > fullwdith *inside* the hook varies. but that's no use to me, since IRL > > that value doesn't work. > > > > so my question is: a) does anyone know of any good examples of assertrepr > > plugins that adjust dynamically to terminal width, and b) what's a good > way > > of writing tests for that? > > > > here's the repo fwiw > > > https://github.com/hjwp/pytest-icdiff/blob/master/tests/test_pytest_icdiff.py > > _______________________________________________ > > pytest-dev mailing list > > pytest-dev@python.org > > https://mail.python.org/mailman/listinfo/pytest-dev > _______________________________________________ > pytest-dev mailing list > pytest-dev@python.org > https://mail.python.org/mailman/listinfo/pytest-dev >
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